This invention relates to the relaxing or straightening of naturally curly hair with strong chemical base and, in particular, to a hair relaxer system and method that ameliorates or inhibits the deposition of exogenous, multivalent metal ion on alkaline, chemically-relaxed hair.
Multivalent metal ions, especially alkaline earth metal cations of calcium and magnesium, when present in the water employed for rinsing the hair during cosmetic hair treatments, such as chemical relaxing, permanent waving of hair and even shampooing, can react with anionic constituents in or on the hair to form water insoluble compounds that undesirably adhere to the hair.
Typically, in the salon or in the home, the source of the rinse water is tap water supplied by the local municipality, and in some instances from limestone wells. In some large metropolitan regions, the hardness of the water contains sufficient calcium, magnesium and other minerals to interfere with cosmetic treatments of human hair.
The adsorption and retention of exogenous, multivalent metal ion minerals on hair can be undesirable because the deposited mineral can visually dull the appearance of the hair, make the tactile and handling characteristics of the hair heavy, coated, and difficult to style, and increase its resistance to or interfere with the effectiveness of certain hair treatments, such as dyeing, bleaching, permanent waving, chemical relaxation or straightening, shampooing, conditioning and the like.
Aside from endogenous trace minerals found in hair and exogenous minerals sorbed from rinse water, exogenous mineral deposits in human hair can also come from cosmetic treatments, topical medications, and environmental pollutants. For example, strong chemical bases are typically employed for chemical hair relaxation at a pH of greater than about 12. Such chemical base treatment can leave numerous negatively charged moieties in the hair, thereby making the chemically-relaxed hair more receptive to adsorption and retention of various multivalent metal ions, especially alkaline earth metal cations, present in the rinse water contacting it immediately following such highly alkaline processing. Mineral deposits can build up on the hair surface undesirably and be further exacerbated by employing hard water rinses during the process of chemically relaxing naturally curly hair especially with xe2x80x9cno-lyexe2x80x9d type hair relaxer compositions.
Commercial chemical hair relaxer products, commonly called xe2x80x9cno-lyexe2x80x9d relaxers, are two-component products that are mixed together just before use to form the strong organic base, guanidinium hydroxide, in situ. One of the two components typically is an activator solution containing guanidine carbonate and the other component is an emulsion creme containing calcium hydroxide in excess of the stoichiometric amount needed to form the strong base. As a result, the admixture contains the byproduct calcium carbonate, and unreacted calcium hydroxide, each of which can form an observable deposit of calcium mineral on the surface of the hair.
Salon practitioners frequently complain about the mineral buildup on chemically-relaxed hair, because it can interfere with the effectiveness of post-relaxer conditioners, hair coloring, and subsequent chemical relaxing hair treatments. Moreover, mineral buildup on the hair generally also dulls the natural sheen of the hair, makes it hard to comb and style, and leaves the scalp and hair feeling dry and rough. Removal of mineral deposit from chemically-relaxed hair presents problems because, following exposure to strong chemical base, the scalp can be vulnerable to irritation and the chemically relaxed hair can be susceptible to weakening damage thereby limiting aggressive removal of mineral ion deposit.
In some prior attempts at resolving the mineral buildup problem, practitioners have resorted to using chemical pre-treatment products, sometimes called xe2x80x9cclarifiersxe2x80x9d or xe2x80x9cprimersxe2x80x9d in the trade, to remove mineral buildup from the hair. These commercial products are available and employed in the form of lotions, shampoos or pre-shampoo sprays, which are applied, sometimes with heat, to the hair before the desired subsequent hair product can be used. However, such chemical pre-treatments, and shampoos in particular, are unsuitable for use just before a chemical relaxation procedure, because they undesirably increase the risk of predisposing the scalp to burning or irritation from the strong chemical base during the subsequent chemical relaxation process.
From industry experience, no-lye type hair relaxers are generally regarded as having a low scalp irritation potential, which has accounted for their popularity and success. However, the increased mineral buildup problem observed with no-lye type hair relaxers has caused salon practitioners, in particular, to avoid using this type of hair relaxer in favor of relaxers containing inorganic caustic base, particularly sodium hydroxide (so-called lye-type relaxers), which tend to have a higher scalp irritation potential, in the belief that mineral buildup would not occur. We have now surprisingly discovered that even when inorganic caustic base containing relaxers are employed, alkaline earth metal minerals, and other multivalent metal ions, when present in the rinse water, also deposit on the chemically relaxed hair during the relaxation process.
Thus, there is an ongoing need to resolve the problem of adsorption and retention by chemically relaxed hair of exogenous multivalent metal ions, and of alkaline earth metal ion, in particular. The hair relaxing system and method of this invention provides a resolution to this problem.
The present invention provides a hair relaxing system and method that ameliorates and inhibits the adsorption and retention by alkaline, chemically-relaxed hair of undesirable exogenous multivalent metal ion present in the chemical relaxer, rinse water or both during the process of relaxing naturally curly hair with compositions having a pH above about 12 containing a hair-relaxing amount of strong chemical base.
In a preferred method aspect, the deposition of exogenous, multivalent metal ion, and calcium and magnesium ion in particular, on alkaline chemically relaxed hair was surprisingly ameliorated and inhibited during the relaxer process by (a) contacting naturally curly hair with a hair relaxing composition having a pH above about pH 12 for a period sufficient to relax all or a portion of the natural curl and then (b) removing the chemical relaxer composition from the alkaline, chemically-relaxed hair employing an aqueous composition having a physiologically tolerable pH and containing an effective chelating amount of at least one exogenous multivalent metal ion chelating agent. It was surprisingly found that concurrently removing the relaxer and contacting alkaline, chemically relaxed hair with the metal ion chelating composition in step (b) for at least about two minutes effectively ameliorated and inhibited sorption and retention of a selected exogenous multivalent metal ion, such that the total content of that metal ion initially present in the hair before the chemical relaxer process was not increased or, increase, if any, was not more than 1.3 fold.
In a particularly preferred method aspect, the foregoing step (b) was carried out during the relaxer process by employing an inventive delivery system adapted for practical salon use. The inventive delivery system beneficially delivers a controlled amount of the metal ion chelating composition concurrently with the rinse water. The beneficial inhibitory effect on metal ion retention is further enhanced by employing soft water preferably having a hardness of not more than 1 ppm. Further the delivery system can be employed under practical salon conditions.
Surprisingly, the adsorption and retention of calcium ion, in particular, by alkaline, chemically-relaxed hair was found to be substantially ameliorated and inhibited by rinsing with an aqueous composition containing not more than about 0.5 weight percent total alkaline earth metal chelating agent employing the inventive delivery system.
In another preferred method aspect, the adsorption and retention of metal ion deposit on alkaline, chemically-relaxed hair was also ameliorated and inhibited in step (b) by (i) removing the chemical relaxer from the hair by rinsing with soft water and then (ii) substantially immediately contacting the water rinsed alkaline, chemically-relaxed hair with a wet wipe impregnated with an aqueous metal ion chelating composition containing an effective chelating amount of at least one multivalent metal ion chelating agent. Alternatively, in the foregoing contact step (b)(ii), an aqueous metal ion chelating composition preferably containing not more than about three weight percent chelating agent can be applied directly to the hair in the form of a rinse or spray.
The present invention beneficially minimizes the exposure of alkaline, chemically-relaxed hair to adsorption and retention of undesirable exogenous multivalent metal ion from the rinse water, chemical relaxer or both during the relaxer process. A particular benefit is that it ameliorates the adsorption and retention of undesirable deposits of exogenous alkaline earth metal ion present in no-lye chemical relaxers. Thus, in the practice of the method of this invention, the measurable total content of multivalent metal ion, and calcium and magnesium ion in particular, in the chemically-relaxed hair is less relative to hair chemically relaxed by conventional methods.
Still another benefit is that the method and delivery system of this invention allows the practitioner to use chemical relaxers, and no-lye type chemical relaxers in particular, in geographic regions where the local tap water supply is hard, or has a high content of multivalent metal ions, thereby avoiding the attendant problems associated with undesirable mineral buildup, and desirably enhancing the aesthetic attributes of the chemically relaxed hair. Additionally, the inventive method provides a resolution of the problem of deposition of alkaline earth metal ion on chemically-relaxed hair which can be carried out during the chemical relaxation process, thereby avoiding the need for separate multi step, mineral stripping chemical hair pre-treatments with potentially skin irritating heat and relatively high levels of metal ion chelating agent.